DAN Medical Frequently Asked Questions

A Runaway Ascent in a Dry Suit

>An inverted diver recovers, but too late to halt her ascent.The incident took place on the last dive of the final day of our 6-day trip to a remote diving area. I and my buddy, (both certified rescue divers with approximately 3 years experience, 150 dives, mostly in drysuit cold water conditions), did our pre-dive checks. On this wall dive, our dive plan was to descend to about 90ft, and traverse the wall until our remaining No Decompression Limit time reached 5 minutes or our pressure reached 1500psi. All dives this week were on air, with dive computers, and safety stops were made on all dives. Water temperatures were in the low 50s F so we wore drysuits. We exited the boat and hit the water, then commenced our descent. When we reached 90 feet my buddy levelled off and I continued my descent to 100 feet to video the wall from below. We were 5-6 minutes into our dive at 90-100 feet when a flash of light caught my attention. My buddy was about 20 feet away, above me and closer to the wall, and I could see she was trying to reverse a feet first ascent by sculling with her hands. She had recovered an upright position but her ascent was continuing. I could see from the air in her suit, a rapid ascent was likely. I began swimming over and up to her, clipping my camera off to a shoulder D-ring. I held my BCD inflator/deflator in my left hand and my dive computer began to beep to warn that my ascent was exceeding 30 feet per minute (10 metres per minute). I added air to my BCD and kicked hard, my hand still on my deflator/inflator control. By now we were likely at 60 feet. I grabbed her fin with my right hand and dumped all the air from my BCD with my left. This was not enough to slow her down. At this point it was a pure runaway ascent. I feared an AGE and began to hyperventilate - short inhale, fast exhale - and hope for the best. Suddenly the water around me was all chaos, as we shot up through the tiny bubbles of our own exhaust. When we were at 15 feet and still firing toward the surface, I made a calculated and conflicted decision. I decided to let go. My ascent immediately stopped and my buddy went to the surface. I made a safe ascent from there, taking 20 seconds or so to reach the surface. She was responsive and alert, with no signs of DCS. Neither of us developed any symptoms following the incident.A rapid ascent from 90 feet depth (~27 m) on the last dive of the final day of a six-day dive trip, having made all dives with air, is a serious situation for any diver to find themselves in. These divers were very fortunate not to develop symptoms of decompression sickness. The key to avoiding a feet-high inversion in a dry suit is to have only enough air in the drysuit to prevent the suit squeezing the diver. The BCD should be used for controlling buoyancy, and the drysuit should be kept minimally inflated. In addition, correct weighting will minimize the amount of air needed to establish neutral buoyancy. A perfectly weighted and trimmed-out drysuit diver should be able to pivot head-down, head-up or horizontal, without ever ascending rapidly to the surface.